The only number is "1" at the top of the metal part stamped D.R.P.
I just returned from my club where we did a chamber cast and confirmed the caliber is 8.15 x 46R. I also took the opportunity to completely disassemble the gun an give it a thorough cleaning. It had been heavily greased intenally at some time in the past. The gunsmithing staff agreed it is in supurb condition and they're after me to get some ammo for it as they all want to fire it!
Jim

The 2nd Amendment IS an unalienable right.